Adapt and survive

Which are the most successful creatures on Earth? Many people would probably plump for Homo sapiens, but a pretty strong case could be made for bacteria: they occupy an astonishing variety of ecological niches - in the oceans, inside living bodies, deep underground in oil deposits, in geysers, possibly even in the clouds. A staggering 50 per cent of the Earth's living tissue (by mass) consists of bacteria. It's a slightly uncomfortable fact that there are more bacteria than human cells in the average person. Not bad for organisms routinely described as 'primitive'.

Of course, bacteria are not primitive at all - they have had nigh on four billion years to evolve into the myriad forms we see today, each with its own specialized way of living. And although they may be genetically and biochemically more simple than multicellular organisms, they have developed some impressive tricks in order to survive and prosper.

Not surprisingly, many species of bacteria have developed a fondness for the human body. While this is not always a problem - in fact, some forms of bacteria are essential to life - bacterial pathogens remain among the most common causes of death on the planet.

The era of antibiotics raised hopes that the scourge of bacteria might be overcome, permanently. Those optimistic early days have long gone. What was overlooked was the basic biology of bacteria. Having survived for four billion years, bacteria have developed a range of highly successful survival strategies, particularly the ability to exchange bits of DNA - a useful way of generating new forms that might be able to colonize new habitats. Unfortunately for us, those mechanisms have been used to spread the genes for resistance to our antibiotics.

Many new insights into bacterial biology have come from genome sequencing projects, the topic of a recent meeting at the Hinxton Hall Conference Centre (see Analysis article entitled [brokenlink] A genome fest). Such projects are a valuable way of generating new leads for treatment or prevention, but they are also emphasizing the uncomfortable truth that bacteria remain formidable enemies. The rapidity of their growth - if one bacterial cell multiplied unchecked it would cover the Earth to a depth of four feet within 24 hours - combined with their ability constantly to generate new variants is an enormous challenge to overcome. It may well mean we will always have to share our planet with them.

Perhaps it is worth remembering that comparatively few bacteria actually cause us harm. Over time, we have adapted to one another and live in harmony. By contrast, many of the most dangerous pathogens are those that have only recently made us their home - rapid death of a host is not in the best interests of a pathogen. These evolutionarily immature relationships are deadly from all perspectives.

So, bacteria are here to stay. Even if we rid ourselves of the current foes, it is inevitable that others will appear at some point in the future. It is a sobering thought, but a worthwhile reminder that humans are not yet masters of all they survey.

The Editor

IMAGE CREDITS
All images, unless otherwise stated below, are from the Wellcome Trust's [brokenlink] Medical Photographic Library. Historical images are from material held in the Wellcome Library for the History and Understanding of Medicine. Material can be viewed at the Wellcome Library or copies obtained through the Medical Photographic Library.

COVER
Image: Adapted from 'Footprint' by Heather Barnett, one of the artworks in the 'Truth and Beauty' exhibition at the Wellcome Trust's TwoTen Exhibition Gallery. The images show colonies of staphylococci bacteria growing on culture medium on which the artist has placed her foot.

NEWS SECTION

•Genome Campus go-ahead
Image: Architect's illustration of the Genome Campus extension.

ANALYSIS SECTION

•Why the fly?
Front image: Drosophila melanogaster. SPL.
Back image: Development of the fly's nervous system (detail shown). Dr Andrea Brand.

•A genome fest
Front image: Dr Julian Parkhill.
Back image: An S. typhi versus E. coli sequence comparison using ACT tool (detail shown) as developed by Dr Parkhill.

•Genomes in flux
Front image: Neisseria meningitidis. SPL.
Back image: Salmonella typhi.

•A molecular identity card
Front image: Dr Martin Maiden.
Back image: Neisseria meningitidis. SPL.

•Magic bullets or deadly missiles
Front image: Poliovirus, the genome of which was recently recreated from scratch. SPL.

RESEARCH DIRECTIONS SECTION

•Scrambled eggs
Front image: Dr Steven Sinkins of the Liverpool School of Tropical Medicine.
Back image: Larvae of Culex mosquitoes. Dr Steven Sinkins, Liverpool School of Tropical Medicine.

•Pump action
Front image: Part of the type IV secretion system for Helicobacter pylori. Professor Gabriel Waksman.
Back image: Professor Gabriel Waksman.

•More than a mouthful
Back image: Oral streptococci (red) adhering to cultured epithelial cells. The cells in the second image are adhering in clumps. Angela Nobbs and Mark Jepson, Bristol Cell Imaging Facility.

POLYPTYCH SECTION

•Living bone
Image: Screen image from the film 'Bone Orchestra'.

•Eaten alive
Images: Bdellovibrio bacterium.

•Truth and beauty
Front image: Dynamic diatom. M I Walker.
Back image: Detail from 'Vessel', an installation by Tracey Holland.

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